The invention is related to a cage for a rolling element bearing, which cage comprises at least one ring shaped body carrying regularly spaced cage bars, each pair of adjacent cage bars defining a cage pocket for accommodating a rolling element.
Such cages are widely known. Their purpose is to maintain a constant, even spacing between the rolling elements.
Usually, rolling element bearings are supplied with an amount of grease for lubricating purposes. Ideally, the grease gradually releases its oil content, thus ensuring an extended lubrication of the bearing. In this respect, it is desirably to apply the grease as close as possible to the parts to be lubricated, e.g. the surface of the rolling elements. In particular, the amounts of grease which are collected on the cage bars are beneficial. These amounts are close to the rolling elements, thus enabling a direct supply of oil thereto.
Centrifugal forces, as occur in service, and limited adhesion however have a negative influence on the grease retention capacity of the cage. As a result, the grease on the cage bars may disappear, and collect in other areas where no supply towards the rolling elements or the raceways of the rings is possible.
The object of the invention is to provide a cage which allows a better lubrication of the bearing. This object is achieved in that least one of the cage bars comprises means for improved retention of grease thereon.
According to the invention, the cage allows more grease to attach itself on the cage bars. Thereby, a prolonged residence time of grease is obtained, as well as a more reliable lubrication of the bearing.
In the cage according to the invention, one or more cage bars may comprise at least one space for accommodation of grease; for instance a cage bar may comprise elements situated radially outside and/or inside, said element(s) defining at least one space for accommodation of grease.
The cage according to the invention may take several forms. According to a first possibility, the cage may consist of a metal, each cage bar being equipped with a protrusion defining a grease retention space. Each cage bar may comprise a bar which is bounded by the protrusions, one being situated radially outside said bar, the other being situated radially inside said bar. This may be a plastic ring shaped body attachable to the cage.
Furthermore, the cage may consist of a plastic material, each protrusion being molded in one part with a cage bar or an attachable ring shaped body.
The invention is also related to a rolling element bearing, comprising an inner ring, an outer ring, a series of rolling elements accommodated in the bearing space defined between the inner ring and the outer ring, and a cage, the cage bars comprising retention means for improved retention of grease thereon, which cage bars together with retention means occupy the available space between the rolling elements.